Your message couldn’t be delivered because you weren’t recognized as a valid sender

If a user continuously sends emails from Office 365 that are classified as spam, they will be restricted from sending any more messages outbound. The user will be listed in the service as a bad outbound sender and will receive a Non-Delivery Report (NDR) that states:

Your message couldn’t be delivered because you weren’t recognized as a valid sender. The most common reason for this is that your email address is suspected of sending spam and it’s no longer allowed to send messages outside of your organization. Contact your email admin for assistance. Remote Server returned ‘550 5.1.8 Access denied, bad outbound sender’

Abou is a Microsoft Azure MVP and IT Pro with over 9 years of experience in the industry.
He focuses on Microsoft technologies. Starting as a support engineer and Microsoft Certified Trainer at IPMC Ghana, he has worked up through the ranks of System Engineering, IT infrastructure Consultant and Cloud Solution Architect. He has deployed several complex solutions for Multi-national Corporations and Governmental Agencies. He is fluent in French and English.
Currently, Abou Conde is a Senior Infrastructure Consultant at Axxend Corporation. Prior to joining Axxend, Abou Conde worked at Global Information Technology Solutions (GITS) IT Company in Ghana, specializing in Enterprise Architecture both on-premise and in the cloud.
Abou is a leader in the IT professional community, Speaker and Blogger.
He is the Founder of Microsoft User Group Ghana Community – The Place where Microsoft Experts Level up. He is also an ambassador for the aOS (Azure, office365, SharePoint) Community.